The present invention relates generally to high security door locks, and more particularly, to such a lock having a cylinder including a solenoid which must be operated to enable operation of the cylinder to unlock an associated door.
A deadlock wherein a bolt is moved only by turning a key or knob, commonly referred to as a deadbolt, is a very popular high security lock for both residential and business applications. In residential applications, the key which comes with or is originally fitted to the lock may be used over the entire life of the lock, or if the residence is sold or a key lost, the owners may choose to have the lock rekeyed. Thus, key changes in residential deadbolts are only infrequently made. In business applications, such is not the case.
Commonly, business deadbolts are rekeyed several times a year due to personnel changes, the loss of a key or simply as a periodic security practice to ensure that keys which may be available to unauthorized people will not operate the lock. Such rekeying operations require a locksmith to reconfigure or change the tumblers in the lock cylinder, and of course, cut new keys corresponding to the new tumbler configuration. While the charges for rekeying a lock may not be a major expense, oftentimes businesses have multiple locks and when one or more locks must be changed a number of times each year, the expenses can become substantial.
Another form of high security door locking device is disclosed in U.S. Pat. No. 3,903,718. The disclosed device comprises two independent lock mechanisms; one, a combination lock, is coupled to the second, a key lock, such that the device can be operated only if an appropriate code is entered into the combination lock and an appropriate key is inserted into the key lock. While this arrangement offers a potential solution to frequent rekeying operations by preventing a key from operating the locking device unless the combination code is also entered, once the code is known, it suffers from the same problems as the deadbolt lock in that the cylinder must be rekeyed and/or the code must be changed. In the disclosed locking device, possibly greater problems and expenses arise in the event of a code change since this requires either replacing the combination portion of the device or considerably more work than the rekeying operation.
Accordingly, a need exists for a high security door locking device which can be quickly changed to prevent entry into the area locked by the device by means of existing keys and/or codes without requiring cylinder rekeying operations or replacement or major changes to portions of the device. It would be further desirable if such a high security door locking device could be provided not only for new installations but also be readily retrofitted into existing locks at a cost which could be recovered within a relatively short period of time as compared to the alternative of having several lock cylinder rekeying operations performed over the same period of time.